Can you explain what locking means when working with a database and why it is needed?

A lock when working with a database is a mechanism that prevents multiple transactions from modifying the same data simultaneously, to avoid conflicts and ensure data integrity.

For example, if two users try to update the same record at the same time, a lock guarantees that the changes will be applied sequentially, not simultaneously, which could lead to data loss.

There are different types of locks:

• Row-level lock — locks a specific record.
• Table-level lock — locks the entire table.
• Optimistic lock — assumes conflicts are rare and checks for them upon saving.
• Pessimistic lock — immediately locks data for the duration of the transaction.

In Python, when working with databases through ORM (e.g., SQLAlchemy), you can use appropriate methods to manage locks.